Method of contracting a hole



Feb. 2, 1965 D. P. WELLES, JR., ETAL 3,167,360

METHOD OF CONTRACTING A HOLE Original Filed April 28, 1958 2Sheets-Sheet 1 I I I 34 Feb. 2, 1965 D. P. WELLES, JR., ETAL 3,167,360

METHOD OF CONTRACTING A HOLE Original Filed April 28, 1958 2Sheets-Sheet 2 INVENTORS. 004/410 1- WZZZZS JR. #67777 [JV/AA 3,167,860METHOD OF CONTRACTING A HOLE Ronald P. Welles, Jr., Rockford, and KeithA. Hill, Rockton, Ill., assignors to Besly-Welles Corporation, SouthBeloit, 11]., a corporation of Illinois Original application Apr. 28,1958, Ser. No. 731,528, riow Patent No. 3,038,253, dated June 12, 1962.Divided and this application Feb. 23, 1961, Ser. No. 102,333 6'Claims.(Cl. 29-556) This is a division of Serial ,No. 731,528, filed Apiil 28,1958, now Patent No. 3,038,253. 7

This invention is in the field of metal working tools ,and methods andis concerned with sizing a cylindrical surface, for example a hole.

In many. situations, it is desirable to reduce the size of a hole in aductile part. The hole may have become worn due to extensive use, forexample the bore of a valve guide, or it might be slightly too largewhen originally made ,due to simple inaccuracies or errors inproduction. In a worn part, it is desirable to decrease the Zefi'ectivediameter of the hole, otherwise the part must be replaced. I On newequipment, the oversized hole may ,be one of many holes in a singlepart, all of the others having the proper diameter, and unless theoversized hole can be reduced, the entire part will have to be scrapped.l

Not only holes but external cylindrical surfaces, such as shafts, rods,etc. have the same problem, and in many situations it is desirable tobuildup or increase the diameter so as to save either an original or anold and worn part.

For purposes of simplicity, we shall refer to only a hole and the use ofa tap type tool. But it should be understood that, in many instances,the entire procedure 'may be reversed or turned inside out and could bea die 1 tap type device which reduces a minimum of torque.

Another object is a hole sizing operation which work hardens the innersurface of the hole.

,Another object is a method of reducing the size of a hole which isparticularly advantageous with ductile metals but not limited thereto.

Other objects will appear from time to time in the ensuing specificationand drawing in which:

FIGURE 1 is a side view, partly in section, of a hole reducing toolprior to entering a hole;

FIGURE 2 is a section along line 22 of FIGURE 1;

FIGURE 3 is an enlarged side view, partly in section, showing the toolentering the hole;

FIGURE 4 is a side view, partly in section, similar to FIGURE 1, showingthe tool fully inserted in the hole;

FIGURE 5 is a side view, partly in section, similar to FIGURE 3, showingthe tool during withdrawal from the hole;

FIGURE 6 is a side view of a modified form of tool;

FIGURE 7 is a bottom view of the tool in FIGURE 6;

FIGURE 8 is a side view of a further variant;

FIGURE 9 is a side view of an additional variation;

FIGURE 10 is a modified form;

FIGURE 11 is a further modification;

United States Patent 0 3,167,869 Patented Feb. 2, 1965 FIGURE 12 is abottom view of FIGURE 11; and

FIGURE 13 is a modification of FIGURE 12.

In FIGURE 1 a tap has been indicated at 10 with a shank 12, a squaredend 14 which may be milled, ground or otherwise formed, and a threadedarea 16 with a burnishing section 18 or the like at the lower end. Thethreaded section or area is shown with a single start V-shaped threaddivided into a full thread area 20, a tapered area 22 and a reverse area24. In the full thread area 20, the thread has a constant thread depthand the pitch diameter, crest diameter and root diameter undulat in aconstant pattern, to be explained hereinbelow. In the tapered area 22the thread is tapered inwardly so that the crest, pitch and rootdiameters uniformly decrease but the thread depth remains constant andis the same as in the full thread area 20. In the reverse area 24, thecrest diameter remains approximately constant while the root and pitchdiameters uniformly increase with the thread depth uniformly decreasing.

The thread forms orturns of the entire threaded section or area 16, aswell as the burnishing section or area 18 at the end, may have reliefareas longitudinally disposed or radially relieved areas. For example,the

thread turns of the tapered area 22 and the full thread area 20 may beformed with varying outside, pitch and root diameters for each turn ofthe thread circumferentially of the tap. The tap is shown as dividedinto three sectors in FIGURE 2, designated A, B and C. The radius atthehigh points A, B and C is at a maximum and varies uniformly in theintermediate areas but with such variation the thread depth remainsconstant.

In the reverse area 24 and burnishing area 18, the radial reliefs aresimilarly applied but the fixed relationship between crest, pitch androot diameters is not maintained. Rather, as will be noted in FIGURES 3and 5, the maximum diameter at the crest of the last turn or thread ofthe full thread area 20 is designated 26. Thereafter, the threads in thetapered area 22 decrease uniformly until the last thread of the taperedarea is reached having a crest diameter designated 28. The thread withthe crest 28.has a full thread depth or the same as the thread depth inthe full thread area 20. In the reverse area 24,'the.crease diameter ofthe threads remains the same or constant while the root diameterincreases, as at 30 and 32, with the thread depth decreasing. It will benoted that all of the threads in between, from 28 to the burnishingsection 18, have an approximately constant crest diameter which is thesame as the diameter 34 of the burnishing section.

The thread formation described above involving a radial relief mayfollow US. Patent No. 2,807,813, issued October 1, 1957., The point isthat the threads are continuous and no cutting edges formed by relieveflutes are present.

The workpiece, designated 36, has a hole with an oversized diameter 37and we prefer that the diameter of the hole be greater than or equal tothe diameter of the burnishing portion 18, and approximately the same asor slightly greaterthan the pitch diameter of the full thread area 20measured at A, B or C in FIGURE 2. Thus, when the tool is inserted androtated in the hole, the burnishing section or area 18 and the reversearea 24 will freely enter, but the tapered area 22 will work the crestof its threads into the side of the hole in a smooth manner that doesnot cut the metal. Rather, the metal displaced by the crowns or crestsof the threads will flow inwardly toward the root of the threads, asshown in FIGURE 3, to establish a thread form in the hole whichapproximates the thread form on the full 7 thread area 20 of the tool.

3 out of the hole and it will be noted thatthe crests 38 of the threadsformed in the hole have a diameter which is less than the diameter ofthe burnishing section 18. As the tool is turned out, theuniformly'increasing roots and 32 in the reverse area 24 will engagethecrests 38 of the thread formation in the hole and, as shown in FIGURE 5,will flow or force the material outwardly until it reaches the diameter34 of the burnishing section. The completed hole willhave an-innersurface resembling that indicated at 40 in FIGURE 5. Since the diameteris ,shrunk somewhat and the material used to reduce the diameter hasbeen taken from the body of the workpiece, voids are left in the form'ofa continuous helical groove or spiral 42. After the tool It) iscompletely backed out, the entire inner surface of the hole will havethis spiral groove 42 and the amount of shrinkage effected will be thedifference between the original diameter of the hole and the diameter 34of the 'may be provided with the radial reliefs indicated'ahove.

It is not necessary to apply the radial reliefs to the shank 12, ofcourse. We'have'shown the relieved'areas as rectilinear," when viewedfrom the side, and axially disposed, but it "should be understood thatsuch relieved areas on one thread might be offset slightly with relationto the relieved areas'on the adjacent threads so that I the radialreliefs would establish a helical or spiral pattern on the entirethreaded'area 16-. 'Wehave also shown only a single start thread, but wemigth use double, triple or what have you.

Another important'point is'that when the 'tool' isinserted and turnedinto ahole, a void will exist:between the full thread area'Zdand'theburnishi'ng section 18 due to the tapered and reverse areas 122 and 24.This void, designated D in FIGURE 3, will extend for. several threadturns and'may be used as a lubricant'reservoin- The clearance around theburnishingisection 18'-Will allow only a small amount of leakage.Excessive lubricant may escape through'the relieved areas; Lubricantwill be entrapped between'the burnishingsection 18 and the full threadarea 20 and will serve to lubricate the burnishing section and toprevent scoring when'the' tool is removed.

In FIGURES 6 and 7, we have shown a variant form inwhich a combined toolwithan area'44 of full'thread flows into a tapered area 46, bothof whichmaybe the same as'the corresponding areas on the tool in JFIG- URES 1through 5. The'end of the tool is provided with a reamer section 48having a pluralityof relieved'lands the full thread area 44. In thiscase, instead of swaging or working the metal back into the'voids, as isdone by the burnishing section in FIGURES 1 through 5, the

excess metal worked up by the full thread is cut off or positivelyremoved by the reamer section which may be formed in a conventionalmanner. The diameter of 50 and grooves '52. Theelfective diameter of thehigh point or cutting edge on the lands of the reamer section should bebetween the pitch. and outside diameters of I the reamer section is suchthat'it will easily pass down the hole, the flutes of the reamer shouldbe the opposite hand from the, fullthreadarea 44.

44 is right-hand, the reamer must be left-hand, in effect.

If the fullthread In FIGURE 8 a variation is shown in which a reamersection, d esi'gnated'54', is disposed'after afull' thread area 56,rather than ahead of it. We position 'a pilot 58 ahead of thetaperedarea 60. The FIGURE 8 tool is 'a straight through instrumentwhile the FIGURE 6 modification is an inand-out tool and may be used ina blind hole. The pilot 58'-is purely optional.

In FIGURE 9 we have shown a further variation in which the full threadarea 62 may. be, as before with a tapered area 64. ing section at thebottom or ahead, as in FIGURES 1 through 5, we put it after the fullthread area, as at 66, and we may use a reverse section 68 between them.The FIGURE 9 tool is therefore a straight through proposition ratherthan an in-and-out tool.

In FIGURE 10 we have 'showna further variation whichinay have afullthread area 70 and, a tapered area 72. A burnishing section 73 isformed at the lower end with a pluralityj of relieved rings 74 whichincrease diameter, as shown, and arenot formed as a helical thread. Inthis case a reversesection may not beused. The point is thateach ring,asthe tool is withdrawn from the. hole, will :work the metal in, theraised areaback into the grooves until the largest ring 74' at thelower-rend establishes the final diameter;

The threads need not necessarily be helical. For example, in FIGURES 11through 13, We have shown a modification in which the, threads 76 are inthe form of axially disposed lands and grooves arranged longitudinal-The material raised fromthe inner surface of the hole will not be in theform of a spiral thread,bi1t rather will be merelyaxially disposedflutes. After'it is raised, it may be returned to the'desir-ed diameterby a burnishing tool or any other sizing portion. I'nEFIGURE 11 we haveshown a burnishing portion or collar'86fwith longitudinalgrooves'gradually merging into this burnish ing section and the tool mayalso have a pilot 87.

. One use; of the FIGURE 11 form is as a stud which may be secured in. ahole. For example, the shank 88' might be threaded at 0 to accept a nut.Instead of;

being turned or screwed into a hole, the; tool might be driven by ahammer or otherwise. The'collar or burnishing portion 86 might beformedas aring'or flange below the threaded area. 78 on or inplace of thepilot 87.. The flutes and relieved areas deform the material on theinner surface of .the hole inwardly into radiallydisposedtfins whichproject within the diameterof the collar portion- Thus, the collar willresist subsequent withdrawal of the stud.

In FIGURE 13 a variant form has been shown in which the flutes orgrooves 92 are formed with .a slighthelix orright-handtwist, when viewedfrom above. As before, annular relief areas 94 are used, and-a collarportion '96 is. disposed below withpa diameter on the order of-thepitclrdiameter. of the portion 98-of'theyribs having the largest outsidediameter. When the stud is driven intoa hole, t-he shaft will turnslightly clockwise, whenwiewed from above, due to the helix or twist ofthe grooves 92. The:

upper endof the shaft may bethreaded {at-100' sothat.

a conventional nut may 'be applied. It should be noted that the threads100are also right-hand, like the helix or twist on the grooves 92. Thus,when the shaft is fully driven into a hole, beit a blind hole orotherwise, and the metal on the inner surface of the holehas' beenworked inwardly by the grooves so that it lies" within the diameter ofthe collar 96, the studwill resist withdrawal. When a nut is turnedfully down on the threaded upper end 100 and is in engagement with theflatsurface.

But instead of havingthe burnisharezseo on top of the hole, the torqueapplied to the stud due to rotation of a nut will be clockwise, which isagainst the direction of the helical interfit between the lands andgrooves 92 and the internal fins formed in the hole.

The use, operation and function of the invention are as follows:

The invention is concerned with a method for varying the size of acylindrical surface, be it a hole, shaft or otherwise. For clarity, thedescription has been and will be confined to hole size reduction.

The general procedure is to draw, force or work spaced areas on theinside of a hole in from the original diameter to a diameter smallerthan that desired, then to work the material outwardly until the desireddiameter is reached. Or the excess material between the smaller diameterand the desired diameter might be cut off or otherwise removed. Ineither case, grooves, either spiral or straight, will be left in theinner surface which may function as passages for fluid, for example alubricant.

The procedure has the advantage that the resulting surface with its newdiameter will be work-hardened. If only a work-hardened surface isdesired when using a tool such as shown in FIGURE 5, the burnishingsection 18 might have an effective diameter which is the same orapproximately the same as the original diameter of the hole. Thediameter of the hole will be returned to the original diameter, and thesurface will be quite hard and wear-resistant. Such a procedure would beparticularly advantageous on stainless steel.

The particular metal-working tool shown has the advantage that therelief areas substantially reduce the torque required to turn or forcethe tool. In FIGURE 2 only three such radial reliefs have been shown,but four, five, six, etc. might be used. Just so the number is not solarge that the radial reliefs have little or no effect. A single startscrew has been shown in FIGURES 1 through 5, but it might be double,triple or what have you. We have referred to and emphasized repair work,but it might be used on original equipment as well.

In the form in FIGURES 1 through 5, the combination of the full threadarea, the tapered area, the reverse area, and the burnishing areaprovides a combination tool which will automatically shrink the hole toa predetermined size. It should be noted, in FIGURE 2, that the radialreliefs are applied to all areas.

The procedure or method has been outlined as including the steps ofworking the material inwardly from the original diameter to a too smalldiameter and thereafter working back or removing the excess to get thedesired diameter which is less than the original. In short, we firstdraw or work the material in, then force it back, or remove it, to thedesired diameter which is between the too large original diameter andthe too small first step diameter. But it is within the scope of ourinvention to size the material accurately when initially working it infrom the original diameter. For example, in FIGURE 3, the root diameter,designated at X, of the full thread form might be precisely at thedesired final diameter, and the thread formation of the full thread areamight be proportioned as to pitch diameter, crest diameter and pitch,relative to the original too large diameter of the hole such that thedisplaced material between the threads would flow in and precisely andexactly coincide, or approximately so, with the root diameter X so thatresizing by the reverse area and burnishing area would not be necessary.

The FIGURE 6 form has the advantage that it is inexpensive. We mightmerely buy a straight shank with a small reamer section, as at 48, atthe end and thereafter apply the full thread area 44 and the taperedarea 46 to it. It also has the advantage that it may be used accuratelyon a blind hole whereas other tools, such as the one in FIGURE 8, arefor a straight through operation.

The direction of the grooves on the tool might be anywhere from a singlestart thread helix, as in FIGURES 1 through 10, to a straight lineargroove, as in FIGURE 11, or any place in between. The grooves might goaround at a 45 or a 60 degree angle, such as in FIG- URE 13.

The sides of the threads in the various areas may be at any suitableangle, for example, 40, 50 or 60 degrees. The tool might be used withworkpieces made of die cast aluminum, brass, bronze, plastics, certainsteels or any ductile or semi-ductile metals. Broadly, a metal should becapable of cold work but the invention is not limited to any particularmaterial. While we have designated ductile materials, since these arethe most easily Worked, other relatively non-ductile materials will alsorespond favorably.

Whereas the preferred form and several variations of the invention havebeen shown and described and suggested, it should be understood thatsuitable additional modifications, changes, substitutions andalterations may be made without departing from the inventionsfundamental theme. We, therefore, wish that the invention beunrestricted, except as by the appended claims.

We claim:

1. A method of reducing the effective diameter of a hole in a particularmaterial from an initial larger diameter to a desired final smallerdiameter, including the steps of applying material working pressureradially outwardly to the inner surface of the hole at uniformly spacedareas and of sufficient intensity to displace the material in such areasinto the intermediate areas, increasing the dimension of each of thespaced areas of applied pressure and the intensity of the pressureapplied thereto to displace material in the intermediate areas inwardlyof the initial larger diameter, continuing the step of increasing thedimension of each of the spaced areas of applied pressure and theintensity of the pressure applied thereto until the diameter of thedisplaced material in the intermediate area is less than the desiredfinal smaller diameter, and sizing the displaced material to the desiredfinal smaller diameter.

2. The method of claim 1 further characterized by and including the stepof applying the material working pressure primarily in a circumferentialdirection at all times.

3. The method of claim 1 further characterized by and including the stepof applying the material working pressure primarily in an axialdirection at all times.

4. The method of claim 1 further characterized in that the sizing stepincludes the step of removing the displaced material in the intermediateareas between the newly formed diameter of the displaced material andthe desired final diameter.

5. The method of claim 1 in which the step of sizing the displacedmaterial to the desired final diameter includes the step of applyingmaterial working pressure to the displaced material in the intermediateareas of sufiicient intensity to displace it back to the desired finaldiameter.

6. The method of claim 1 further characterized by and including the stepof connecting the uniformly spaced areas of applied pressure into auniform continuous helix.

References (Zited in the file of this patent UNITED STATES PATENTS2,349,863 Hallberg May 30, 1944 2,625,065 Trishman Jan. 13, 19532,703,419 Barth Mar. 8, 1955 2,810,191 Hanna Oct. 22, 1957 3,012,317Wolfe Dec. 12, 1961 3,050,755 Welles Aug. 28, 1962

1. A METHOD OF REDUCING THE EFFECTIVE DIAMETER OF A HOLE IN A PARTICULARMATERIAL FROM AN INITIAL LARGER DIAMETER TO A DESIRED FINAL SMALLERDIAMETER, INCLUDING THE STEPS OF APPLYING MATERIAL WORKING PRESSURERADIALLY OUTWARDLY TO THE INNER SURFACE OF THE HOLE AT UNIFORMLY SPACEDAREAS AND OF SUFFICIENT INTENSITY TO DISPLACE THE MATERIAL IN SUCH AREASINTO THE INTERMEDIATE AREAS, INCREASING THE DIMENSION OF EACH OF THESPACED AREAS OF APPLIED PRESSURE AND THE INTENSITY OF THE PRESSUREAPPLIED THERETO TO DISPLACE MATERIAL IN THE INTERMEDIATE AREAS INWARDLYOF THE INITIAL LARGER DIAMETER, CONTINUING THE STEP OF INCREASING THEDIMENSION OF EACH OF THE SPACED AREAS OF APPLIED PRESSURE AND THEINTENSITY OF THE PRESSURE APPLIED THERETO UNTIL THE DIAMETER OF THEDISPLACED MATERIAL IN THE INTERMEDIATE AREA IS LESS THAN THE DESIREDFINAL SMALLER DIAMETER, AND SIZING THE DISPLACED MATERIAL TO THE DESIREDFINAL SMALLER DIAMETER.